Often times it is desirable to provide braking mechanisms on rotating equipment to expend the kinetic energies stored in driven members and thereby prevent extended freewheeling of those members after a driving source has been disconnected. It is apparent that in certain situations, such as the driving of rotary cutters in lawnmowers, choppers or other forms of equipment having rotary members more or less accessible to an operator, that manually operable braking devices to stop such rotary members could be employed with an included disadvantage that the operator must continually remember to engage and disengage the brake during operation. Often such devices fall into disuse.
Others have provided overrunning clutches which do not provide a braking action on rotating members but rather produce an audible sound when the driving source is disconnected which may alert the operator that the rotary member is still in motion.
In the related applications, Ser. No. 133,641 and Ser. No. 296,462, self-actuating braking mechanism similar to that disclosed herein are provided. Specifically, these mechanisms, one of which is shown for reference in FIG. 1, comprise a drive member A having an input pulley attached thereto and having a lower braking surface thereon, which threadedly engages an output shaft B having a cutting member C and means for limiting the upward axial movement of the drive member A when it rotates on the threads of the shaft. The downward axial movement of the drive member on the shaft is limited by a nonrotary braking member D springingly supported in the shaft housing.
When power flows from the input pulley to rotate the cutting member, the drive member A rotates on the shaft B and moves axially upward until it contacts the limiting means on the shaft. At this point most of the driving force is transmitted through the threads of the shaft and drives the cutting member. When the power is interrupted, the momentum of the cutting member C causes the shaft to rotate in the drive member A moving it axially downward until its braking surface contacts the braking surface on the brake member D. At this point, a braking force is developed which is transmitted through the threads to the shaft and cutting member until they stop rotating.
While these mechanisms perform their intended functions, they also present some problems. First, the threads on the shaft are required to transmit most of the driving force transmitted through the mechanism and all of the braking force. This condition is conductive to excessive wear of the threads, especially if lubrication is neglected, which may lead not only to a condition rendering the braking action inoperative but possibly to total failure of the mechanism.
A second problem with these mechanisms is that the input pulley, being connected to the drive member A, moves up and down during starting and braking. Since the drive belt is usually in a transient condition during these times, its tension generally being increased or decreased to transmit or interrupt power to the cutting mechanism, the movement of the pulley may cause the belt to be thrown. Moreover, a buildup of debris beneath the pulley could prevent the braking mechanism from operating.
Accordingly, it is an object of the invention described herein to provide a self-actuating drive-brake mechanism wherein the driving force is transmitted from the input drive to the output drive and cutter substantially independently of the means used to shift the braking means to the braking position.
It is further an object of the invention to provide a connection between the input drive and the output shaft and cutter which is axially static during all conditions of operation.
Other objects and features of the present invention will become more fully apparent in view of the following detailed description taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the inventive concepts hereinafter disclosed.